OPC UA文档的最后一章（即第18章），讲述发布订阅（Publish Subscribe）的定义和使用，也是OPC UA里很重要的功能。关于发布订阅原理，可以网上搜索，最大特点就是发布者和订阅者是解耦的。
本文主要讲述如何运行一个简单的Broker-less demo，即无代理的PubSub。
一 原理图
使用UDP Multicast功能来实现Broker-less发布订阅，如下图
发布者向multicast地址224.0.5.1发送消息，多个订阅者可以从224.0.5.1获取消息。中间没有代理。
二 配置和编译open62541
本文使用的open62541版本是1.1.1，运行环境：debian 10 （ubuntu也是一样）
首先打开源码目录下CMakeLists.txt，找到UA_ENABLE_PUBSUB，如下，
改成ON，然后在源码目录下创建build目录，cd进入，并执行下面命令，
cmake .. && make
三 代码
本文代码都是来自open62541自带example，即tutorial_pubsub_publish.c和tutorial_pubsub_subscribe.c，未作改动
tutorial_pubsub_publish.c如下，其发布的内容是系统时间
/* This work is licensed under a Creative Commons CCZero 1.0 Universal License.
* See http://creativecommons.org/publicdomain/zero/1.0/ for more information. */
/**
* .. _pubsub-tutorial:
*
* Working with Publish/Subscribe
* ------------------------------
*
* Work in progress: This Tutorial will be continuously extended during the next
* PubSub batches. More details about the PubSub extension and corresponding
* open62541 API are located here: :ref:`pubsub`.
*
* Publishing Fields
* ^^^^^^^^^^^^^^^^^
* The PubSub publish example demonstrate the simplest way to publish
* informations from the information model over UDP multicast using the UADP
* encoding.
*
* **Connection handling**
*
* PubSubConnections can be created and deleted on runtime. More details about
* the system preconfiguration and connection can be found in
* ``tutorial_pubsub_connection.c``.
*/
#include <open62541/plugin/log_stdout.h>
#include <open62541/plugin/pubsub_ethernet.h>
#include <open62541/plugin/pubsub_udp.h>
#include <open62541/server.h>
#include <open62541/server_config_default.h>
#include <signal.h>
UA_NodeId connectionIdent, publishedDataSetIdent, writerGroupIdent;
static void
addPubSubConnection(UA_Server *server, UA_String *transportProfile,
UA_NetworkAddressUrlDataType *networkAddressUrl){
/* Details about the connection configuration and handling are located
* in the pubsub connection tutorial */
UA_PubSubConnectionConfig connectionConfig;
memset(&connectionConfig, 0, sizeof(connectionConfig));
connectionConfig.name = UA_STRING("UADP Connection 1");
connectionConfig.transportProfileUri = *transportProfile;
connectionConfig.enabled = UA_TRUE;
UA_Variant_setScalar(&connectionConfig.address, networkAddressUrl,
&UA_TYPES[UA_TYPES_NETWORKADDRESSURLDATATYPE]);
/* Changed to static publisherId from random generation to identify
* the publisher on Subscriber side */
connectionConfig.publisherId.numeric = 2234;
UA_Server_addPubSubConnection(server, &connectionConfig, &connectionIdent);
}
/**
* **PublishedDataSet handling**
*
* The PublishedDataSet (PDS) and PubSubConnection are the toplevel entities and
* can exist alone. The PDS contains the collection of the published fields. All
* other PubSub elements are directly or indirectly linked with the PDS or
* connection. */
static void
addPublishedDataSet(UA_Server *server) {
/* The PublishedDataSetConfig contains all necessary public
* informations for the creation of a new PublishedDataSet */
UA_PublishedDataSetConfig publishedDataSetConfig;
memset(&publishedDataSetConfig, 0, sizeof(UA_PublishedDataSetConfig));
publishedDataSetConfig.publishedDataSetType = UA_PUBSUB_DATASET_PUBLISHEDITEMS;
publishedDataSetConfig.name = UA_STRING("Demo PDS");
/* Create new PublishedDataSet based on the PublishedDataSetConfig. */
UA_Server_addPublishedDataSet(server, &publishedDataSetConfig, &publishedDataSetIdent);
}
/**
* **DataSetField handling**
*
* The DataSetField (DSF) is part of the PDS and describes exactly one published
* field. */
static void
addDataSetField(UA_Server *server) {
/* Add a field to the previous created PublishedDataSet */
UA_NodeId dataSetFieldIdent;
UA_DataSetFieldConfig dataSetFieldConfig;
memset(&dataSetFieldConfig, 0, sizeof(UA_DataSetFieldConfig));
dataSetFieldConfig.dataSetFieldType = UA_PUBSUB_DATASETFIELD_VARIABLE;
dataSetFieldConfig.field.variable.fieldNameAlias = UA_STRING("Server localtime");
dataSetFieldConfig.field.variable.promotedField = UA_FALSE;
dataSetFieldConfig.field.variable.publishParameters.publishedVariable =
UA_NODEID_NUMERIC(0, UA_NS0ID_SERVER_SERVERSTATUS_CURRENTTIME);
dataSetFieldConfig.field.variable.publishParameters.attributeId = UA_ATTRIBUTEID_VALUE;
UA_Server_addDataSetField(server, publishedDataSetIdent,
&dataSetFieldConfig, &dataSetFieldIdent);
}
/**
* **WriterGroup handling**
*
* The WriterGroup (WG) is part of the connection and contains the primary
* configuration parameters for the message creation. */
static void
addWriterGroup(UA_Server *server) {
/* Now we create a new WriterGroupConfig and add the group to the existing
* PubSubConnection. */
UA_WriterGroupConfig writerGroupConfig;
memset(&writerGroupConfig, 0, sizeof(UA_WriterGroupConfig));
writerGroupConfig.name = UA_STRING("Demo WriterGroup");
writerGroupConfig.publishingInterval = 100;
writerGroupConfig.enabled = UA_FALSE;
writerGroupConfig.writerGroupId = 100;
writerGroupConfig.encodingMimeType = UA_PUBSUB_ENCODING_UADP;
writerGroupConfig.messageSettings.encoding = UA_EXTENSIONOBJECT_DECODED;
writerGroupConfig.messageSettings.content.decoded.type = &UA_TYPES[UA_TYPES_UADPWRITERGROUPMESSAGEDATATYPE];
/* The configuration flags for the messages are encapsulated inside the
* message- and transport settings extension objects. These extension
* objects are defined by the standard. e.g.
* UadpWriterGroupMessageDataType */
UA_UadpWriterGroupMessageDataType *writerGroupMessage = UA_UadpWriterGroupMessageDataType_new();
/* Change message settings of writerGroup to send PublisherId,
* WriterGroupId in GroupHeader and DataSetWriterId in PayloadHeader
* of NetworkMessage */
writerGroupMessage->networkMessageContentMask = (UA_UadpNetworkMessageContentMask)(UA_UADPNETWORKMESSAGECONTENTMASK_PUBLISHERID |
(UA_UadpNetworkMessageContentMask)UA_UADPNETWORKMESSAGECONTENTMASK_GROUPHEADER |
(UA_UadpNetworkMessageContentMask)UA_UADPNETWORKMESSAGECONTENTMASK_WRITERGROUPID |
(UA_UadpNetworkMessageContentMask)UA_UADPNETWORKMESSAGECONTENTMASK_PAYLOADHEADER);
writerGroupConfig.messageSettings.content.decoded.data = writerGroupMessage;
UA_Server_addWriterGroup(server, connectionIdent, &writerGroupConfig, &writerGroupIdent);
UA_Server_setWriterGroupOperational(server, writerGroupIdent);
UA_UadpWriterGroupMessageDataType_delete(writerGroupMessage);
}
/**
* **DataSetWriter handling**
*
* A DataSetWriter (DSW) is the glue between the WG and the PDS. The DSW is
* linked to exactly one PDS and contains additional informations for the
* message generation. */
static void
addDataSetWriter(UA_Server *server) {
/* We need now a DataSetWriter within the WriterGroup. This means we must
* create a new DataSetWriterConfig and add call the addWriterGroup function. */
UA_NodeId dataSetWriterIdent;
UA_DataSetWriterConfig dataSetWriterConfig;
memset(&dataSetWriterConfig, 0, sizeof(UA_DataSetWriterConfig));
dataSetWriterConfig.name = UA_STRING("Demo DataSetWriter");
dataSetWriterConfig.dataSetWriterId = 62541;
dataSetWriterConfig.keyFrameCount = 10;
UA_Server_addDataSetWriter(server, writerGroupIdent, publishedDataSetIdent,
&dataSetWriterConfig, &dataSetWriterIdent);
}
/**
* That's it! You're now publishing the selected fields. Open a packet
* inspection tool of trust e.g. wireshark and take a look on the outgoing
* packages. The following graphic figures out the packages created by this
* tutorial.
*
* .. figure:: ua-wireshark-pubsub.png
* :figwidth: 100 %
* :alt: OPC UA PubSub communication in wireshark
*
* The open62541 subscriber API will be released later. If you want to process
* the the datagrams, take a look on the ua_network_pubsub_networkmessage.c
* which already contains the decoding code for UADP messages.
*
* It follows the main server code, making use of the above definitions. */
UA_Boolean running = true;
static void stopHandler(int sign) {
UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_SERVER, "received ctrl-c");
running = false;
}
static int run(UA_String *transportProfile,
UA_NetworkAddressUrlDataType *networkAddressUrl) {
signal(SIGINT, stopHandler);
signal(SIGTERM, stopHandler);
UA_Server *server = UA_Server_new();
UA_ServerConfig *config = UA_Server_getConfig(server);
UA_ServerConfig_setDefault(config);
/* Details about the connection configuration and handling are located in
* the pubsub connection tutorial */
config->pubsubTransportLayers =
(UA_PubSubTransportLayer *) UA_calloc(2, sizeof(UA_PubSubTransportLayer));
if(!config->pubsubTransportLayers) {
UA_Server_delete(server);
return EXIT_FAILURE;
}
config->pubsubTransportLayers[0] = UA_PubSubTransportLayerUDPMP();
config->pubsubTransportLayersSize++;
#ifdef UA_ENABLE_PUBSUB_ETH_UADP
config->pubsubTransportLayers[1] = UA_PubSubTransportLayerEthernet();
config->pubsubTransportLayersSize++;
#endif
addPubSubConnection(server, transportProfile, networkAddressUrl);
addPublishedDataSet(server);
addDataSetField(server);
addWriterGroup(server);
addDataSetWriter(server);
UA_StatusCode retval = UA_Server_run(server, &running);
UA_Server_delete(server);
return retval == UA_STATUSCODE_GOOD ? EXIT_SUCCESS : EXIT_FAILURE;
}
static void
usage(char *progname) {
printf("usage: %s <uri> [device]\n", progname);
}
int main(int argc, char **argv) {
UA_String transportProfile =
UA_STRING("http://opcfoundation.org/UA-Profile/Transport/pubsub-udp-uadp");
UA_NetworkAddressUrlDataType networkAddressUrl =
{
UA_STRING_NULL , UA_STRING("opc.udp://224.0.0.22:4840/")};
if (argc > 1) {
if (strcmp(argv[1], "-h") == 0) {
usage(argv[0]);
return EXIT_SUCCESS;
} else if (strncmp(argv[1], "opc.udp://", 10) == 0) {
networkAddressUrl.url = UA_STRING(argv[1]);
} else if (strncmp(argv[1], "opc.eth://", 10) == 0) {
transportProfile =
UA_STRING("http://opcfoundation.org/UA-Profile/Transport/pubsub-eth-uadp");
if (argc < 3) {
printf("Error: UADP/ETH needs an interface name\n");
return EXIT_FAILURE;
}
networkAddressUrl.networkInterface = UA_STRING(argv[2]);
networkAddressUrl.url = UA_STRING(argv[1]);
} else {
printf("Error: unknown URI\n");
return EXIT_FAILURE;
}
}
return run(&transportProfile, &networkAddressUrl);
}
tutorial_pubsub_subscribe.c如下，其订阅了4个值：一个系统时间，一个int32变量，一个int64变量和一个bool变量。并把这些订阅的item映射到OPC UA Server的地址空间里。
/* This work is licensed under a Creative Commons CCZero 1.0 Universal License.
* See http://creativecommons.org/publicdomain/zero/1.0/ for more information.
*
* Copyright (c) 2019 Kalycito Infotech Private Limited
*/
/**
* IMPORTANT ANNOUNCEMENT
* The PubSub Subscriber API is currently not finished. This example can be used
* to receive and display values that are published by tutorial_pubsub_publish
* example in the TargetVariables of Subscriber Information Model .
*/
#include <open62541/plugin/log_stdout.h>
#include <open62541/plugin/pubsub_udp.h>
#include <open62541/server.h>
#include <open62541/server_config_default.h>
#include <open62541/types_generated.h>
#include "ua_pubsub.h"
#ifdef UA_ENABLE_PUBSUB_ETH_UADP
#include <open62541/plugin/pubsub_ethernet.h>
#endif
#include <stdio.h>
#include <signal.h>
#include <stdlib.h>
UA_NodeId connectionIdentifier;
UA_NodeId readerGroupIdentifier;
UA_NodeId readerIdentifier;
UA_DataSetReaderConfig readerConfig;
static void fillTestDataSetMetaData(UA_DataSetMetaDataType *pMetaData);
/* Add new connection to the server */
static UA_StatusCode
addPubSubConnection(UA_Server *server, UA_String *transportProfile,
UA_NetworkAddressUrlDataType *networkAddressUrl) {
if((server == NULL) || (transportProfile == NULL) ||
(networkAddressUrl == NULL)) {
return UA_STATUSCODE_BADINTERNALERROR;
}
UA_StatusCode retval = UA_STATUSCODE_GOOD;
/* Configuration creation for the connection */
UA_PubSubConnectionConfig connectionConfig;
memset (&connectionConfig, 0, sizeof(UA_PubSubConnectionConfig));
connectionConfig.name = UA_STRING("UDPMC Connection 1");
connectionConfig.transportProfileUri = *transportProfile;
connectionConfig.enabled = UA_TRUE;
UA_Variant_setScalar(&connectionConfig.address, networkAddressUrl,
&UA_TYPES[UA_TYPES_NETWORKADDRESSURLDATATYPE]);
connectionConfig.publisherId.numeric = UA_UInt32_random ();
retval |= UA_Server_addPubSubConnection (server, &connectionConfig, &connectionIdentifier);
if (retval != UA_STATUSCODE_GOOD) {
return retval;
}
retval |= UA_PubSubConnection_regist(server, &connectionIdentifier);
return retval;
}
/* Add ReaderGroup to the created connection */
static UA_StatusCode
addReaderGroup(UA_Server *server) {
if(server == NULL) {
return UA_STATUSCODE_BADINTERNALERROR;
}
UA_StatusCode retval = UA_STATUSCODE_GOOD;
UA_ReaderGroupConfig readerGroupConfig;
memset (&readerGroupConfig, 0, sizeof(UA_ReaderGroupConfig));
readerGroupConfig.name = UA_STRING("ReaderGroup1");
retval |= UA_Server_addReaderGroup(server, connectionIdentifier, &readerGroupConfig,
&readerGroupIdentifier);
return retval;
}
/* Add DataSetReader to the ReaderGroup */
static UA_StatusCode
addDataSetReader(UA_Server *server) {
if(server == NULL) {
return UA_STATUSCODE_BADINTERNALERROR;
}
UA_StatusCode retval = UA_STATUSCODE_GOOD;
memset (&readerConfig, 0, sizeof(UA_DataSetReaderConfig));
readerConfig.name = UA_STRING("DataSet Reader 1");
/* Parameters to filter which DataSetMessage has to be processed
* by the DataSetReader */
/* The following parameters are used to show that the data published by
* tutorial_pubsub_publish.c is being subscribed and is being updated in
* the information model */
UA_UInt16 publisherIdentifier = 2234;
readerConfig.publisherId.type = &UA_TYPES[UA_TYPES_UINT16];
readerConfig.publisherId.data = &publisherIdentifier;
readerConfig.writerGroupId = 100;
readerConfig.dataSetWriterId = 62541;
/* Setting up Meta data configuration in DataSetReader */
fillTestDataSetMetaData(&readerConfig.dataSetMetaData);
retval |= UA_Server_addDataSetReader(server, readerGroupIdentifier, &readerConfig,
&readerIdentifier);
return retval;
}
/* Set SubscribedDataSet type to TargetVariables data type
* Add subscribedvariables to the DataSetReader */
static UA_StatusCode
addSubscribedVariables (UA_Server *server, UA_NodeId dataSetReaderId) {
if(server == NULL) {
return UA_STATUSCODE_BADINTERNALERROR;
}
UA_StatusCode retval = UA_STATUSCODE_GOOD;
UA_NodeId folderId;
UA_String folderName = readerConfig.dataSetMetaData.name;
UA_ObjectAttributes oAttr = UA_ObjectAttributes_default;
UA_QualifiedName folderBrowseName;
if(folderName.length > 0) {
oAttr.displayName.locale = UA_STRING ("en-US");
oAttr.displayName.text = folderName;
folderBrowseName.namespaceIndex = 1;
folderBrowseName.name = folderName;
}
else {
oAttr.displayName = UA_LOCALIZEDTEXT ("en-US", "Subscribed Variables");
folderBrowseName = UA_QUALIFIEDNAME (1, "Subscribed Variables");
}
UA_Server_addObjectNode (server, UA_NODEID_NULL,
UA_NODEID_NUMERIC (0, UA_NS0ID_OBJECTSFOLDER),
UA_NODEID_NUMERIC (0, UA_NS0ID_ORGANIZES),
folderBrowseName, UA_NODEID_NUMERIC (0,
UA_NS0ID_BASEOBJECTTYPE), oAttr, NULL, &folderId);
retval |= UA_Server_DataSetReader_addTargetVariables (server, &folderId,
dataSetReaderId,
UA_PUBSUB_SDS_TARGET);
UA_free(readerConfig.dataSetMetaData.fields);
return retval;
}
/* Define MetaData for TargetVariables */
static void fillTestDataSetMetaData(UA_DataSetMetaDataType *pMetaData) {
if(pMetaData == NULL) {
return;
}
UA_DataSetMetaDataType_init (pMetaData);
pMetaData->name = UA_STRING ("DataSet 1");
/* Static definition of number of fields size to 4 to create four different
* targetVariables of distinct datatype
* Currently the publisher sends only DateTime data type */
pMetaData->fieldsSize = 4;
pMetaData->fields = (UA_FieldMetaData*)UA_Array_new (pMetaData->fieldsSize,
&UA_TYPES[UA_TYPES_FIELDMETADATA]);
/* DateTime DataType */
UA_FieldMetaData_init (&pMetaData->fields[0]);
UA_NodeId_copy (&UA_TYPES[UA_TYPES_DATETIME].typeId,
&pMetaData->fields[0].dataType);
pMetaData->fields[0].builtInType = UA_NS0ID_DATETIME;
pMetaData->fields[0].name = UA_STRING ("DateTime");
pMetaData->fields[0].valueRank = -1; /* scalar */
/* Int32 DataType */
UA_FieldMetaData_init (&pMetaData->fields[1]);
UA_NodeId_copy(&UA_TYPES[UA_TYPES_INT32].typeId,
&pMetaData->fields[1].dataType);
pMetaData->fields[1].builtInType = UA_NS0ID_INT32;
pMetaData->fields[1].name = UA_STRING ("Int32");
pMetaData->fields[1].valueRank = -1; /* scalar */
/* Int64 DataType */
UA_FieldMetaData_init (&pMetaData->fields[2]);
UA_NodeId_copy(&UA_TYPES[UA_TYPES_INT64].typeId,
&pMetaData->fields[2].dataType);
pMetaData->fields[2].builtInType = UA_NS0ID_INT64;
pMetaData->fields[2].name = UA_STRING ("Int64");
pMetaData->fields[2].valueRank = -1; /* scalar */
/* Boolean DataType */
UA_FieldMetaData_init (&pMetaData->fields[3]);
UA_NodeId_copy (&UA_TYPES[UA_TYPES_BOOLEAN].typeId,
&pMetaData->fields[3].dataType);
pMetaData->fields[3].builtInType = UA_NS0ID_BOOLEAN;
pMetaData->fields[3].name = UA_STRING ("BoolToggle");
pMetaData->fields[3].valueRank = -1; /* scalar */
}
UA_Boolean running = true;
static void stopHandler(int sign) {
UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_SERVER, "received ctrl-c");
running = false;
}
static int
run(UA_String *transportProfile, UA_NetworkAddressUrlDataType *networkAddressUrl) {
signal(SIGINT, stopHandler);
signal(SIGTERM, stopHandler);
/* Return value initialized to Status Good */
UA_StatusCode retval = UA_STATUSCODE_GOOD;
UA_Server *server = UA_Server_new();
UA_ServerConfig *config = UA_Server_getConfig(server);
UA_ServerConfig_setMinimal(config, 4801, NULL);
/* Add the PubSub network layer implementation to the server config.
* The TransportLayer is acting as factory to create new connections
* on runtime. Details about the PubSubTransportLayer can be found inside the
* tutorial_pubsub_connection */
config->pubsubTransportLayers = (UA_PubSubTransportLayer *)
UA_calloc(2, sizeof(UA_PubSubTransportLayer));
if(!config->pubsubTransportLayers) {
UA_Server_delete(server);
return EXIT_FAILURE;
}
config->pubsubTransportLayers[0] = UA_PubSubTransportLayerUDPMP();
config->pubsubTransportLayersSize++;
#ifdef UA_ENABLE_PUBSUB_ETH_UADP
config->pubsubTransportLayers[1] = UA_PubSubTransportLayerEthernet();
config->pubsubTransportLayersSize++;
#endif
/* API calls */
/* Add PubSubConnection */
retval |= addPubSubConnection(server, transportProfile, networkAddressUrl);
if (retval != UA_STATUSCODE_GOOD)
return EXIT_FAILURE;
/* Add ReaderGroup to the created PubSubConnection */
retval |= addReaderGroup(server);
if (retval != UA_STATUSCODE_GOOD)
return EXIT_FAILURE;
/* Add DataSetReader to the created ReaderGroup */
retval |= addDataSetReader(server);
if (retval != UA_STATUSCODE_GOOD)
return EXIT_FAILURE;
/* Add SubscribedVariables to the created DataSetReader */
retval |= addSubscribedVariables(server, readerIdentifier);
if (retval != UA_STATUSCODE_GOOD)
return EXIT_FAILURE;
retval = UA_Server_run(server, &running);
UA_Server_delete(server);
return retval == UA_STATUSCODE_GOOD ? EXIT_SUCCESS : EXIT_FAILURE;
}
static void
usage(char *progname) {
printf("usage: %s <uri> [device]\n", progname);
}
int main(int argc, char **argv) {
UA_String transportProfile = UA_STRING("http://opcfoundation.org/UA-Profile/Transport/pubsub-udp-uadp");
UA_NetworkAddressUrlDataType networkAddressUrl = {
UA_STRING_NULL , UA_STRING("opc.udp://224.0.0.22:4840/")};
if(argc > 1) {
if(strcmp(argv[1], "-h") == 0) {
usage(argv[0]);
return EXIT_SUCCESS;
} else if(strncmp(argv[1], "opc.udp://", 10) == 0) {
networkAddressUrl.url = UA_STRING(argv[1]);
} else if(strncmp(argv[1], "opc.eth://", 10) == 0) {
transportProfile =
UA_STRING("http://opcfoundation.org/UA-Profile/Transport/pubsub-eth-uadp");
if(argc < 3) {
printf("Error: UADP/ETH needs an interface name\n");
return EXIT_FAILURE;
}
networkAddressUrl.networkInterface = UA_STRING(argv[2]);
networkAddressUrl.url = UA_STRING(argv[1]);
} else {
printf ("Error: unknown URI\n");
return EXIT_FAILURE;
}
}
return run(&transportProfile, &networkAddressUrl);
}
四 运行
首先创建工程，先新建一个pubsub_broker-less目录，然后执行下面操做，
- 在pubsub_broker-less目录下创建open62541目录
- 把open62541源码目录下的arch目录、deps目录、include目录、plugins目录和src目录拷贝到pubsub_broker-less目录下的open62541目录里
- 把open62541源码目录下build目录里的src_generated目录也拷贝到上一步的位置
- 把open62541源码目录下build目录里libopen62541.a也拷贝到上一步的位置
PS：为什么这么麻烦？因为没有使用UA_ENABLE_AMALGAMATION，即使开启了这个选项，编译时还是需要引入一些别的与pubsub相关的文件，所以就索性把需要的文件一股脑的拷贝过来（也带了很多不相关的文件，读者有时间的话可以自己尝试精简下）
接下来，在pubsub_broker-less目录下创建build目录和src目录，并把tutorial_pubsub_publish.c和tutorial_pubsub_subscribe.c拷贝到src目录里，最后新建一个CMakeLists.txt
整体工程目录结构如下，
CMakeLists.txt内容如下，
cmake_minimum_required (VERSION 3.5)
project (pubsub_broker-less_demo)
include_directories(${
CMAKE_CURRENT_SOURCE_DIR}/open62541/include)
include_directories(${
CMAKE_CURRENT_SOURCE_DIR}/open62541/src_generated)
include_directories(${
CMAKE_CURRENT_SOURCE_DIR}/open62541/plugins/include)
include_directories(${
CMAKE_CURRENT_SOURCE_DIR}/open62541/arch)
include_directories(${
CMAKE_CURRENT_SOURCE_DIR}/open62541/deps)
include_directories(${
CMAKE_CURRENT_SOURCE_DIR}/open62541/src/pubsub)
find_library(OPEN62541_LIB libopen62541.a PATHS ${
CMAKE_CURRENT_SOURCE_DIR}/open62541/)
add_executable(publisher ${
CMAKE_CURRENT_SOURCE_DIR}/src/tutorial_pubsub_publish.c)
target_link_libraries(publisher ${
OPEN62541_LIB} pthread)
add_executable(subscriber ${
CMAKE_CURRENT_SOURCE_DIR}/src/tutorial_pubsub_subscribe.c)
target_link_libraries(subscriber ${
OPEN62541_LIB} pthread)
cd到build目录下，执行下面命令，
cmake .. && make
编译成功后，在build目录下可以看到生成了publisher和subscriber
先运行publisher，
./publisher opc.udp://224.0.5.1:4840/
接着运行subscriber
./subscriber opc.udp://224.0.5.1:4840/
注意，PubSub模式中由于双方是解耦的，所以哪个先运行都是无关紧要的。
最后就是观察一下双方的通信情况了
1. 观察publisher发布的报文消息
使用wireshark进行观察
sudo apt install wireshark
sudo wireshark
运行后选择电脑的网卡并在filter区输入udp就可以了，截图如下，可以看出publish间隔是100ms，每个消息传播的数据长度是39个字节，还有地址信息等等
2. 观察subscriber订阅的消息
使用UaExpert进行观察，代码里subscriber的server地址是opc.tcp://xxx:4801/，使用UaExpert连接ok后如下，
DataSet 1目录下是订阅项映射过来的4个变量，可以前面的描述一致。
publisher发布的是系统时间，那么subscriber订阅的系统时间也会进行变化，把DataSet 1目录下的DateTime变量拖到Data Access View中，可以发现是不断在更新的
说明运行OK
五 总结
本文主要讲述了如何运行一个Broker-less发布订阅的简单demo，并没做过多的代码分析，里面涉及很多概念，具体可以参考官方文档还有代码注释。
运行这个demo也是试了很久才搞定，pubsub功能很重要也很强大，需要依赖的东西也不少。
如果有问题，欢迎在评论区留言。谢谢。